Step 1: Identify the gas law to be used.
Since temperature is constant, Boyle’s law applies.
\[
P_1V_1 = P_2V_2
\]
Step 2: Substitute the given values.
\[
P_1 = 1\ \text{bar}, \quad V_1 = 500\ \text{dm}^3
\]
\[
V_2 = 200\ \text{dm}^3
\]
Step 3: Calculate final pressure.
\[
P_2 = \frac{P_1V_1}{V_2} = \frac{1 \times 500}{200}
\]
\[
P_2 = 2.5\ \text{bar}
\]
Step 4: Conclusion.
Minimum pressure required is 2.5 bar.